1. Field of the Invention
The present invention relates to an imaging system and a method for detecting a target object.
2. Discussion of the Background
An imaging system has been known with which skin color areas are detected to extract face area candidates by image analysis, distance information of an imaging optical system is obtained to estimate a maximum size of a face that is to be actually taken into an image, and any skin color area that exceeds the maximum size is determined not to be a face area and excluded from the face area candidates (for example, see Japanese Unexamined Patent Publication No. 2004-185555). The contents of Japanese Unexamined Patent Publication No. 2004-185555 are incorporated herein by reference in their entirety.
However, with the above-described conventional system, a maximum size of a face is estimated based on a focal length when an imaging optical system is focused. Accordingly, distance information of the imaging optical system is unknown before the focusing, which results in a disadvantage that it is not possible to accurately estimate a size of a person's face. Moreover, a problem exists even after the focusing that, while it is possible to accurately estimate the size of a person's face on which the system is focused, it is not possible to accurately estimate the size of a person's face on which the system is not focused because there is an error in the distance information of the imaging optical system.